Posts Tagged ‘physics presentation’


good times were had

December 19, 2008

Several presentations were given. One on the fact that people don’t give a shit about online security because they’re irrational and shortsighted, all they want is convenience. So if you’re planning on being an evil business man, don’t bother with online store security. I should have known.

Then the new ZFS file system by Sun for virtual server storage was presented, and compared to EXT3. I actually learned a lot from that presentation, like how RAID is used in parity checking. Also, the ZFS file system actually just uses a data pool for all drives and volumes (making volumes a thing of the past) managed by the ZIF I/O system, which is integrated with the actual partition manager. Partitions become invisible and irrelevant, and all the super blocks are managed by “uber blocks”. It’s all very interesting, JFGI.

I totally awesomified everything with the physics presentation. I feel like…. really good. It went really smoothly. Interesting because I had a nervous breakdown right beforehand and fucking puked. In the bathroom, but I do have a horrible fear of public speaking.

But then the Othello game team presented, and they were actually really good. The most amazing of the AI scripts shown by the advanced non-linear algorithms class was the one by Iain. It took the game timer and computed how many seconds it has to make this move (realistic approximation) then spends exactly that amount of time. It does a possible moves benefit/penalty difference tree search, but to speed it up it does alpha beta pruning to remove sub trees with first layer search expensive nodes to within a certain tolerance (each new layer search given the most promising avenues in Layman’s terms.) The result is a beautifully executed compromise between the fastest computed and most predictive model, where for each new search layer moves are eliminated until the best is given or time runs out in which case the best of the moves so far in the search is used. This means that the longer it is given, the better the move it will make, but because it is entirely scalable to time as it is ACTIVELY AWARE of time, it will always make a move at least one layer of predictive strategy deep, but ALMOST ALWAYS MORE.

Yeah. Fucking genius. It beat EVERYONE, and their relatively puny AI programs.

So, yeah, I would say that I may have been the highlight, but it was hard to to Iain’s AI program. I was blown away.


Then, we headed down to Eric’s Aaron’s house (I don’t have their names down yet blargh!) and played rock band for a while. I got to sing Metallica lol. After a while we went to a dinner with Dr. Liow and some other professors I don’t know, Chinese food for all! It was pretty sweet. We talked about how awesome Chrono Trigger is and why A* is still quite often the best pathfinder if you prune the search properly for large maps with area zoning. Also, there was some discussion as to why romance novels are low grade girl porn, and agreed to have another AI face off. Plus there was specifically Colombian coffee at the place, that is my favorite variety! It was all around awesome. Then on the way home we were almost killed in an accident because of the freezing rain. But we didn’t hit anybody or vice-versa. We DID do some awesome donuts though.


looks like talk is a go + preparation of examples

October 25, 2008

So, it looks like the talk is gonna be a GO.  :3  We’re reserving a room for some coming Tuesday.  I’m basically preparing like a crazy person, because I need to make this count.  Think about it… this could literally evolve in to a free ride for me.

I’ve got my slides, peer reviewed them with a friend, (who was surprisingly supportive,) and got my presentation planned.  Now I’m working on the software aspects of my presentation.  I want the examples program to be at least half full of numbered demos.  I’ve got a Pinchinco like example with balls falling through triangular pegs, but I also want some more practical demonstrations.  Varying restitution, varying friction, dominos, maybe a character control application demo.  I fixed the timing code in both the testbed and the examples program, so that’s all good.

It’s a race to the finish line, and this time it’s not on a motherfucking circle track!  There’s actual progress to be made!  Why couldn’t highschool ever be like that?


time of impact islands + talk presentation thingy

October 23, 2008

HEY HEY HEY HEY HEY HEY HEY HEY *gets smacked down*


You’re not guessing.  I’ll tell you!  I’m actually giving a talk at Columbia College about my physics project.  Here’s essentially what I got off Dr. Liow.  Dr. Liow is probably one of the best people to recognize anything you do, because he seems like he’d be honest if he didn’t like what you’ve done.  In an email he was all: “Your program is interesting.  Do you want to give a talk about it during lunch, blabitty bloo, blabitty bloo, blabitty bloo, it’s totally unofficial, blabitty bloo, it’s in a room with some people, blabitty bloo, blabitty bloo, this is totally gonna be like a presentation during lunch so omg r u interested?”  Man, I hope he doesn’t read that.  Meh, I don’t really care.  Anyway, I was all “shit yeah” and he’s all “omg I haven’t even checked my email yet so I haven’t responded yet.”  So I’m still waiting for a reply.  But I’m psyched, and I really like the idea of publicising my physics engine, if even on a local scale, so I’m definitely going to be there.  I’m gonna make slides, demos, tacos, nachos, and paper mache!  Okay, actually just slides and demos.  Can you tell I’m giddy?  Huh?  Is it showing?  ANSWER ME!  YAAAAAAAYYYYY!!!!!!!!

This is pretty awesome.  All I’m sayin’.

NOW.  On the topic of actual work that I’m doing on physics.  You may have thought about time of impact and how it would slow everything down.  You’re damn right it will.  The question is, how can we optimize it as much as possible?  In the most accurate TOI model, you find the pending collision with the smallest TOI, advance by that amount, (of course setting a minimum fraction of total timestep so we don’t get stuck at toi==0.0 forever,) handle collisions normally, run the impulse solver, and repeat until the timestep is done.  But what about Joe McStranded off in the distance who won’t collide with anyone for at least a dozen frames?  Should we waste time sub stepping him?  NO.

The solution: islands.  This is a technique I am shamelessly stealing from Bullet Physics.  But we all stand on the shoulders of giants, right?  Anyway, an island is essentially a field of objects which will all interact with one another in the next frame.  An island of objects are all linked by constraints, contacts, and bounding box sweeps.  Anything which may collide with other bodies in the island or be affected by a body in the island is in, basically. This means the loners are all omitted from the expensive sub steps in time of impact solving, and this also means smaller islands who will do less sub steps than the bigger ones.

So, as for sweep algorithms, I have circles down, and I’m trying to do the MSA-sweep now.  I’m not exactly sure of how it will turn out on rotating bodies, as I’ve said before.  I may wind up using the conservative advancement method.  I’ve said this before, I’m just rehashing it.

Think about using islands in your own work.